Conventional combine and forage harvesters have a header assembly for harvesting crop from a field and feeding it into a processing mechanism. For crops such as barley, rye, oats and wheat, the header assembly usually comprises a header having a primary cutter head that cuts the crop, and a reel and two lateral augers that draw the cut crop into a central feeder (also known as a straw elevator). The augers drive the crop from the ends of the header towards the feeder which then raises the crop into the mouth or infeed of the crop processing mechanism of the harvester.
In a combine harvester, the processing mechanism may typically comprise a threshing cylinder for separating the grain from the straw and the chaff. After the crop has been threshed, the grain passes over oscillating sieves that separate it from the chaff and it is stored in a grain tank. The straw on the other hand is transported by straw walkers or a separating cylinder to the rear of the harvester where it is either chopped and dispersed with the chaff or laid down in swaths or windrows for later baling.
It is known from U.S. Pat. No. 2,401,513 and EP 0 212 185 for a header assembly for a harvester having a header as described above to be provided with a secondary scissor-action cutter head mounted on a support frame trailed behind the primary cutter head for cutting stalks left behind by the primary cutter head. The secondary cutter head may be supported by ground engaging rollers or skids.